Characterizing GHZ Correlations in Nondegenerate Parametric Oscillation via Phase Measurements

Greenberger-Horne-Zeilinger states and few-body Hamiltonians

The generation of Greenberger-Horne-Zeilinger (GHZ) states is a crucial problem in quantum information. We derive general conditions for obtaining GHZ states as eigenstates of a Hamiltonian. In general, degeneracy cannot be avoided if the Hamiltonian contains m-body interaction terms with m<=2 and a number of qubits strictly larger than 4. As an application, we explicitly construct a two-body 4-qubit Hamiltonian and a three-body 5-qubit Hamiltonian that exhibit a GHZ as a nondegenerate eigenstate.

Temporal interference effects in noncollinear and frequency-nondegenerate spontaneous parametric down-conversion

We consider regimes of Spontaneous Parametric Down-Conversion both noncollinear and nondegenerate in frequencies. Parameters characterizing degrees of noncollinearity and of nondgeneracy are defined, and they are shown to be not independent of each other. At a given degree of nondegeneracy the emitted photons are shown to propagate along two different cones opening angles of which are determined by the degree of nondegeneracy. Based on this, the degree of nondegeneracy can be controlled by means of the angular selection of photons, e.g., with the help of appropriately installed slits. For such…

Efficient and spectrally bright source of polarization-entangled photons

We demonstrate an efficient fiber-coupled source of nondegenerate polarization entangled photons at 795 and 1609 nm using bidirectionally pumped parametric down-conversion in bulk periodically poled lithium niobate. The single-mode source has an inferred bandwidth of 50 GHz and a spectral brightness of 300 pairs/s/GHz/mW of pump power that is suitable for narrowband applications such as entanglement transfer from photonic to atomic qubits.

表征高维多体纠缠超越Greenberger-Horne-Zeilinger保真度

Characterizing high-dimensional multipartite entanglement beyond Greenberger-Horne-Zeilinger fidelities

本文提出了一种新的方法，用于表征高维多体纠缠态，超越了传统的GHZ保真度，并通过实验验证其在高维纠缠态认证中的有效性与简便性。

Entanglement and Discord of superposition of Greenberger-Horne-Zeilinger states

We calculate the analytic expression for geometric measure of entanglement for arbitrary superposition of two $N$-qubit canonical orthonormal Greenberger-Horne-Zeilinger ($GHZ$) states and the same for two $W$ states. In course of characterizing all kinds of nonclassical correlations, explicit formula for quantum discord (via relative entropy) for the former class of states has been presented. Contrary to the $GHZ$ state, the closest separable state to the $W$ state is not classical. Therefore, in this case the discord is different from the relative entropy of entanglement. We conjecture that …

通过相空间可视化表征噪声对多体纠缠的影响

Characterizing Noise Effects on Multipartite Entanglement via Phase-Space Visualization

本文通过相空间可视化研究噪声对多体纠缠态的影响，利用自旋Wigner函数分析纠缠结构在噪声下的响应，为量子计算中的抗噪声协议设计提供理论支持。